U.S. patent application number 15/052006 was filed with the patent office on 2016-09-08 for projector and control method for projector.
This patent application is currently assigned to SEIKO EPSON CORPORATION. The applicant listed for this patent is SEIKO EPSON CORPORATION. Invention is credited to Junichi SUZUKI, Toru TERASHIMA.
Application Number | 20160261833 15/052006 |
Document ID | / |
Family ID | 56851216 |
Filed Date | 2016-09-08 |
United States Patent
Application |
20160261833 |
Kind Code |
A1 |
SUZUKI; Junichi ; et
al. |
September 8, 2016 |
PROJECTOR AND CONTROL METHOD FOR PROJECTOR
Abstract
In a projector, a reflection mirror configured to reflect light
emitted from a discharge lamp is disposed on a first end of a
discharge lamp main body, a first electrode is disposed on the
first end side, each of a first AC period and a second AC period
alternately includes a first polarity period in which the first
electrode serves as an anode and a second polarity period in which
a second electrode serves as an anode, a controller causes a period
to transition from the first AC period to the second AC period in a
case where an input reception unit receives a stop operation on the
projector, and an absolute value of a driving current of the second
polarity period in the second AC period is greater than an absolute
value of the driving current of the second polarity period in the
first AC period.
Inventors: |
SUZUKI; Junichi;
(Matsumoto-Shi, JP) ; TERASHIMA; Toru;
(Matsumoto-Shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SEIKO EPSON CORPORATION |
Tokyo |
|
JP |
|
|
Assignee: |
SEIKO EPSON CORPORATION
Tokyo
JP
|
Family ID: |
56851216 |
Appl. No.: |
15/052006 |
Filed: |
February 24, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H05B 47/10 20200101;
G03B 21/2026 20130101; H05B 41/36 20130101; Y02B 20/00 20130101;
H05B 41/2828 20130101; H04N 9/3144 20130101; H04N 9/3155 20130101;
Y02B 20/186 20130101 |
International
Class: |
H04N 9/31 20060101
H04N009/31; H05B 41/36 20060101 H05B041/36; H05B 41/282 20060101
H05B041/282 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 4, 2015 |
JP |
2015-042885 |
Mar 4, 2015 |
JP |
2015-042886 |
Claims
1. A projector comprising: a discharge lamp configured to emit
light; a reflection mirror configured to reflect the light emitted
from the discharge lamp in a predetermined direction; a discharge
lamp driving unit configured to supply a driving current to the
discharge lamp; a controller configured to control the discharge
lamp driving unit; an input reception unit configured to receive a
predetermined operation; a light modulation device configured to
modulate the light emitted from the discharge lamp according to an
image signal; and a projection optical device configured to project
light modulated by the light modulation device, wherein the
discharge lamp includes a discharge lamp main body that has a
discharge space therein, and a first electrode and a second
electrode that protrude in the discharge space, wherein the
reflection mirror is attached to a first end of the discharge lamp
main body, wherein the first electrode is disposed on the first end
side, wherein the second electrode is disposed on a second end side
of the discharge lamp main body opposite to the first end, wherein
the driving current includes a first AC period and a second AC
period in which an alternating current is supplied to the discharge
lamp, wherein each of the first AC period and the second AC period
alternately includes a first polarity period in which the first
electrode serves as an anode and a second polarity period in which
the second electrode serves as an anode, wherein, in a case where
the input reception unit receives a stop operation on the
projector, the controller causes a period in which an alternating
current is supplied to the discharge lamp to transition from the
first AC period to the second AC period, and wherein an absolute
value of the driving current of the second polarity period in the
second AC period is greater than an absolute value of the driving
current of the second polarity period in the first AC period.
2. The projector according to claim 1, wherein the absolute value
of the driving current of the second polarity period in the second
AC period is 0.8 times or greater and 1.25 times or smaller than an
absolute value of the driving current obtained when rating power is
supplied to the discharge lamp.
3. The projector according to claim 1, wherein an absolute value of
the driving current of the first polarity period in the second AC
period is smaller than an absolute value of the driving current of
the first polarity period in the first AC period.
4. The projector according to claim 3, wherein a mean value of
driving power supplied to the discharge lamp in the second AC
period is the same as a value of driving power supplied to the
discharge lamp in the first AC period.
5. A projector comprising: a discharge lamp configured to emit
light; a reflection mirror configured to reflect the light emitted
from the discharge lamp in a predetermined direction; a discharge
lamp driving unit configured to supple a driving current to the
discharge lamp; a controller configured to control the discharge
lamp driving unit; an input reception unit configured to receive a
predetermined operation; a light modulation device configured to
modulate the light emitted from the discharge lamp according to an
image signal; and a projection optical device configured to project
light modulated by the light modulation device, wherein the
discharge lamp includes a discharge lamp main body that has a
discharge space therein, and a first electrode and a second
electrode that protrude in the discharge space, wherein the
reflection mirror is attached to a first end of the discharge lamp
main body, wherein the first electrode is disposed on the first end
side, wherein the second electrode is disposed on a second end side
of the discharge lamp main body opposite to the first end, wherein
the driving current includes a first AC period and a second AC
period in which an alternating current is supplied to the discharge
lamp, wherein each of the first AC period and the second AC period
alternately includes a first polarity period in which the first
electrode serves as an anode and a second polarity period in which
the second electrode serves as an anode, wherein, in a case where
the input reception unit receives a stop operation on the
projector, the controller causes a period in which an alternating
current is supplied to the discharge lamp to transition from the
first AC period to the second AC period, and wherein a length of
the second polarity period in the second AC period is larger than a
length of the first polarity period in the second AC period.
6. The projector according to claim 1, wherein the length of the
second AC period is 5.0 ms or more and 10 s or less.
7. The projector according to claim 5, wherein the length of the
second AC period is 5.0 ms or more and 10 s or less.
8. The projector according to claim 1, wherein the stop operation
includes a first stop operation and a second stop operation which
is performed temporally later than the first stop operation, and
wherein the second AC period is provided in at least a partial
period between the first stop operation and the second stop
operation.
9. The projector according to claim 5, wherein the stop operation
includes a first stop operation and a second stop operation which
is performed temporally later than the first stop operation, and
wherein the second AC period is provided in at least a partial
period between the first stop operation and the second stop
operation.
10. The projector according to claim 8, wherein, in a case where
the input reception unit receives the first stop operation, the
controller performs a checking operation for checking whether or
not operation stoppage of the projector is necessary.
11. The projector according to claim 9, wherein, in a case where
the input reception unit receives the first stop operation, the
controller performs a checking operation for checking whether or
not operation stoppage of the projector is necessary.
12. The projector according to claim 8, wherein, in a case where
the input reception unit receives the second stop operation, the
controller controls the discharge lamp driving unit to stop the
supply of the driving current to the discharge lamp.
13. The projector according to claim 9, wherein, in a case where
the input reception unit receives the second stop operation, the
controller controls the discharge lamp driving unit to stop the
supply of the driving current to the discharge lamp.
14. The projector according to claim 1, further comprising: a
cooling unit configured to cool the discharge lamp, wherein the
controller in the first AC period, drives the cooling unit with a
first output which is set according to driving power supplied to
the discharge lamp, and in at least a part of the second AC period,
drives the cooling unit with a second output which is more than the
first output.
15. The projector according to claim 5, further comprising: a
cooling unit configured to cool the discharge lamp, wherein the
controller in the first AC period, drives the cooling unit with a
first output which is set according to driving power supplied to
the discharge lamp, and in at least a part of the second AC period,
drives the cooling unit with a second output which is more than the
first output.
16. The projector according to claim 1, further comprising: a
cooling unit configured to cool the reflection mirror, wherein the
controller in the first AC period, drives the cooling unit with a
first output which is set according to driving power supplied to
the discharge lamp, and in at least a part of the second AC period,
drives the cooling unit with a second output which is more than the
first output.
17. The projector according to claim 5, further comprising: a
cooling unit configured to cool the reflection mirror, wherein the
controller in the first AC period, drives the cooling unit with a
first output which is set according to driving power supplied to
the discharge lamp, and in at least a part of the second AC period,
drives the cooling unit with a second output which is more than the
first output.
18. The projector according to claim 1, wherein a frequency of the
driving current in the second AC period is higher than a frequency
of the driving current in the first AC period.
19. The projector according to claim 5, wherein a frequency of the
driving current in the second AC period is higher than a frequency
of the driving current in the first AC period.
20. A control method for a projector including a discharge lamp
configured to emit light, a reflection mirror configured to reflect
the light emitted from the discharge lamp, and an input reception
unit configured to receive a predetermined operation, the discharge
lamp having a discharge lamp main body that has a discharge space
therein, and a first electrode and a second electrode that protrude
in the discharge space, the reflection mirror being attached to a
first end of the discharge lamp main body, the first electrode
being disposed on the first end side, and the second electrode
being disposed on a second end side of the discharge lamp main body
opposite to the first end, the control method comprising: supplying
a driving current including a first AC period and a second AC
period in which an alternating current is supplied to the discharge
lamp and which alternately include a first polarity period in which
the first electrode serves as an anode and a second polarity period
in which the second electrode serves as an anode respectively, and
performing transition of a period in which an alternating current
is supplied to the discharge lamp from the first AC period to the
second AC period, in a case where the input reception unit receives
a stop operation on the projector, wherein an absolute value of the
driving current of the second polarity period in the second AC
period is greater than an absolute value of the driving current of
the second polarity period in the first AC period.
Description
CROSS-REFERENCE
[0001] This application is based upon and claims the benefit of
priority from Japanese Patent Application Nos. 2015-042885 and
2015-042886, both filed Mar. 4, 2015; the entire contents of which
are incorporated herein by reference.
BACKGROUND
[0002] 1. Technical Field
[0003] The present invention relates to a projector, and a control
method for the projector.
[0004] 2. Related Art
[0005] If an operation of a projector is stopped, the temperature
of a discharge lamp provided in the projector decreases. Thus,
mercury enclosed in the discharge lamp may condense and may be
attached to an inner wall or electrodes of the discharge lamp. At
this time, a mercury bridge may be generated as a result of the
electrodes being connected to each other via mercury. If the
mercury bridge is generated, the electrodes are short-circuited to
each other, and thus the discharge lamp cannot be lighted.
[0006] In relation to this problem, Japanese Patent No. 4070420
discloses a method in which, in order to prevent a mercury bridge,
lamp power supplied to electrodes is reduced to the extent to which
arc discharge does not disappear in a state in which a discharge
lamp transitions from a lighting state to a put-out state, and thus
a light emitting tube portion is cooled to the extent to which
mercury condenses.
[0007] However, in the above-described method, there is a problem
in that time is required to cool the light emitting tube portion to
the extent to which mercury condenses. For this reason, even if a
user performs a stop operation on the projector, the projector
continuously performs lighting at low power during that time, and
thus there is a problem in that convenience of the projector is
reduced.
SUMMARY
[0008] An advantage of some aspects of the invention is to provide
a projector having a configuration capable of minimizing a mercury
bridge and minimizing deterioration in convenience, and a control
method for the projector.
[0009] A projector according to one aspect of the invention
includes a discharge lamp configured to emit light; a reflection
mirror configured to reflect the light emitted from the discharge
lamp in a predetermined direction; a discharge lamp driving unit
configured to supply a driving current to the discharge lamp; a
controller configured to control the discharge lamp driving unit;
an input reception unit configured to receive a predetermined
operation; a light modulation device configured to modulation the
light emitted from the discharge lamp according to an image signal;
and a projection optical device configured to project light
modulated by the light modulation device in which the discharge
lamp includes a discharge lamp main body that has a discharge space
therein; and a first electrode and a second electrode that protrude
in the discharge space, in which the reflection mirror is attached
to a first end of the discharge lamp main body, in which the first
electrode is disposed on the first end side, the second electrode
is disposed on a second end side of the discharge lamp main body
opposite to the first end, the driving current includes a first AC
period and a second AC period in which an alternating current is
supplied to the discharge lamp, and each of the first AC period and
the second AC period alternately includes a first polarity period
in which the first electrode serves as an anode and a second
polarity period in which the second electrode serves as an anode.
In a case where the input reception unit receives a stop operation
on the projector, the controller causes a period in which an
alternating current is supplied to the discharge lamp to transition
from the first AC period to the second AC period, and an absolute
value of the driving current of the second polarity period in the
second AC period is greater than an absolute value of the driving
current of the second polarity period in the first AC period.
[0010] According to the projector according to the aspect of the
invention, an absolute value of the driving current of the second
polarity period in the second AC period is greater than an absolute
value of the driving current of the second polarity period in the
first AC period. For this reason, it is possible to heat the second
electrode in the second AC period and thus to increase the
temperature of the second electrode. Consequently, it is possible
to lengthen a time period until the temperature of the second
electrode becomes lower than the temperature of the discharge lamp
main body after the discharge lamp is put out. As a result, the
temperature of the discharge lamp main body is likely to become
lower than the boiling point of mercury before the temperature of
the second electrode becomes lower than the temperature of the
discharge lamp main body. Therefore, mercury is likely to condense
on an inner wall of the discharge lamp main body, and thus it is
possible to minimize the generation of a mercury bridge.
[0011] If an absolute value of the driving current of the second
polarity period in the second AC period is increased, it is
possible to make the temperature of the second electrode high in a
relatively short time period. Therefore, it is possible to put out
the discharge lamp in a relatively short time period after the
input reception unit receives a stop operation. Consequently, it is
possible to minimize deterioration in convenience of the
projector.
[0012] As mentioned above, according to the projector according to
the aspect of the invention, it is possible to provide the
projector having a configuration capable of minimizing a mercury
bridge and of minimizing deterioration in convenience.
[0013] A projector according to one aspect of the invention
includes a discharge lamp configured to emit light; a reflection
mirror configured to reflect the light emitted from the discharge
lamp in a predetermined direction; a discharge lamp driving unit
configured to supply a driving current to the discharge lamp; a
controller configured to control the discharge lamp driving unit;
an input reception unit configured to receive a predetermined
operation; a light modulation device configured to modulate the
light emitted from the discharge lamp according to an image signal;
and a projection optical device configured to project light
modulated by the light modulation device, in which the discharge
lamp includes a discharge lamp main body that has a discharge space
therein; and a first electrode and a second electrode that protrude
in the discharge space, the reflection mirror is attached to a
first end of the discharge lamp main body, the first electrode is
disposed on the first end side, the second electrode is disposed on
a second end side of the discharge lamp main body opposite to the
first end, the driving current includes a first AC period and a
second AC period in which an alternating current is supplied to the
discharge lamp, and each of the first AC period and the second AC
period alternately includes a first polarity period in which the
first electrode serves as an anode and a second polarity period in
which the second electrode serves as an anode. In a case where the
input reception unit receives a stop operation on the projector,
the controller causes a period in which an alternating current is
supplied to the discharge lamp to transition from the first AC
period to the second AC period, and a length of the second polarity
period in the second AC period is larger than a length of the first
polarity period in the second AC period.
[0014] According to the projector according to the aspect of the
invention, a length of the second polarity period in the second AC
period is larger than a length of the first polarity period in the
second AC period. For this reason, it is possible to heat the
second electrode in the second AC period and thus to increase the
temperature of the second electrode. Consequently, it is possible
to lengthen a time period until the temperature of the second
electrode becomes lower than the temperature of the discharge lamp
main body after the discharge lamp is put out. As a result, the
temperature of the discharge lamp main body is likely to become
lower than the boiling point of mercury before the temperature of
the second electrode becomes lower than the temperature of the
discharge lamp main body. Therefore, mercury is likely to condense
on an inner wall of the discharge lamp main body, and thus it is
possible to minimize the generation of a mercury bridge.
[0015] According to the projector according to the aspect of the
invention, it is possible to make the temperature of the second
electrode high in a relatively short time period in the second AC
period. Therefore, it is possible to stop an operation of the
projector in a relatively short time period after the input
reception unit receives a stop operation. Consequently, it is
possible to minimize deterioration in convenience of the
projector.
[0016] As mentioned above, according to the projector according to
the aspect of the invention, it is possible to provide the
projector having a configuration capable of minimizing a mercury
bridge and of minimizing deterioration in convenience.
[0017] The aspect of the invention may be configured such that the
length of the second AC period is 5.0 ms or more and 10 s or
less.
[0018] According to the configuration, it is possible to
appropriately heat the second electrode in the second AC period and
also to minimize deterioration in convenience of the projector.
[0019] The aspect of the invention may be configured such that the
absolute value of the driving current of the second polarity period
in the second AC period is 0.8 times or greater and 1.25 times or
smaller than an absolute value of the driving current obtained when
rating power is supplied to the discharge lamp.
[0020] According to the configuration, it is possible to easily
heat the second electrode in a short time period.
[0021] The aspect of the invention may be configured such that the
stop operation includes a first stop operation and a second stop
operation which is performed temporally later than the first stop
operation, and the second AC period is provided in at least a
partial period between the first stop operation and the second stop
operation.
[0022] According to the configuration, since an operation of the
projector can be stopped right after a user performs the second
stop operation, it is possible to further minimize deterioration in
convenience of the projector.
[0023] The aspect of the invention may be configured such that, in
a case where the input reception unit receives the first stop
operation, the controller performs a checking operation for
checking whether or not operation stoppage of the projector is
necessary.
[0024] According to the configuration, it is possible to prevent a
user from wrongly stop an operation of the projector.
[0025] The aspect of the invention may be configured such that, in
a case where the input reception unit receives the second stop
operation, the controller controls the discharge lamp driving unit
to stop the supply of the driving current to the discharge
lamp.
[0026] According to the configuration, it is possible to minimize
deterioration in convenience of the projector.
[0027] The aspect of the invention may be configured such that the
projector further includes a cooling unit configured to cool the
discharge lamp, and the controller, in the first AC period, drives
the cooling unit with an first output which is set according to
driving power supplied to the discharge lamp, and in at least a
part of the second AC period, drives the cooling unit with a second
output which is more than the first output.
[0028] According to the configuration, it is possible to further
minimize the generation of a mercury bridge.
[0029] The aspect of the invention may be configured such that the
projector further includes a cooling unit configured to cool the
reflection mirror, and the controller, in the first AC period,
drives the cooling unit with an first output which is set according
to driving power supplied to the discharge lamp, and in at least a
part of the second AC period, drives the cooling unit with a second
output which is more than the first output.
[0030] According to the configuration, it is possible to further
minimize the generation of a mercury bridge.
[0031] The aspect of the invention may be configured such that an
absolute value of the driving current of the first polarity period
in the second AC period is smaller than an absolute value of the
driving current of the first polarity period in the first AC
period.
[0032] According to the configuration, it is possible to increase
the temperature of only the second electrode of the first electrode
and the second electrode, and also to minimize the occurrence of
flickering in the discharge lamp by preventing an increase in an
average power amount in the second AC period relative to an average
power amount in the first AC period.
[0033] The aspect of the invention may be configured such that a
mean value of driving power supplied to the discharge lamp in the
second AC period is the same as a value of driving power supplied
to the discharge lamp in the first AC period.
[0034] According to the configuration, it is possible to minimize
the occurrence of flickering in the discharge lamp.
[0035] The aspect of the invention may be configured such that a
frequency of the driving current in the second AC period is higher
than a frequency of the driving current in the first AC period.
[0036] According to the configuration, a length of the second
polarity period in one cycle of the driving current of the second
AC period can be made smaller than a length of the second polarity
period in one cycle of the driving current of the first AC period.
For this reason, it is possible to prevent a protrusion at a tip of
the second electrode from being considerably melted and deformed
due to an increase in an absolute value of the driving current in
the second AC period. Consequently, it is possible to stably and
easily increase the temperature of the second electrode in the
second AC period.
[0037] A control method for a projector according to one aspect of
the invention, the projector including a discharge lamp configured
to emit light, a reflection mirror configured to reflect the light
emitted from the discharge lamp, and an input reception unit
configured to receive a predetermined operation, the discharge lamp
having a discharge lamp main body that has a discharge space
therein, and a first electrode and a second electrode that protrude
in the discharge space, the reflection mirror being attached to a
first end of the discharge lamp main body, the first electrode
being disposed on the first end side, and the second electrode
being disposed on a second end side of the discharge lamp main body
opposite to the first end, the control method includes supplying a
driving current including a first AC period and a second AC period
in which an alternating current is supplied to the discharge lamp
and which alternately include a first polarity period in which the
first electrode serves as an anode and a second polarity period in
which the second electrode serves as an anode respectively. In a
case where the input reception unit receives a stop operation on
the projector, performing transition of a period in which an
alternating current is supplied to the discharge lamp from the
first AC period to the second AC period, and an absolute value of
the driving current of the second polarity period in the second AC
period is greater than an absolute value of the driving current of
the second polarity period in the first AC period.
[0038] According to the control method for the projector according
to the aspect of the invention, it is possible to provide the
projector having a configuration capable of minimizing a mercury
bridge and of minimizing deterioration in convenience in the same
manner as described above.
[0039] A control method for a projector according to one aspect of
the invention, the projector including a discharge lamp configured
to emit light, a reflection mirror configured to reflect the light
emitted from the discharge lamp, and an input reception unit
configured to receive a predetermined operation, the discharge lamp
having a discharge lamp main body that has a discharge space
therein, and a first electrode and a second electrode that protrude
in the discharge space, the reflection mirror being attached to a
first end of the discharge lamp main body, the first electrode
being disposed on the first end side, and the second electrode
being disposed on a second end side of the discharge lamp main body
opposite to the first end, the control method includes supplying a
driving current including a first AC period and a second AC period
in which an alternating current is supplied to the discharge lamp
and which alternately include a first polarity period in which the
first electrode serves as an anode and a second polarity period in
which the second electrode serves as an anode respectively. In a
case where the input reception unit receives a stop operation on
the projector, performing transition of a period in which an
alternating current is supplied to the discharge lamp from the
first AC period to the second AC period, and a length of the second
polarity period in the second AC period is larger than a length of
the first polarity period in the second AC period.
[0040] According to the control method for the projector according
to the aspect of the invention, it is possible to provide the
projector having a configuration capable of minimizing a mercury
bridge and of minimizing deterioration in convenience in the same
manner as described above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] The invention will be described with reference to the
accompanying drawings, wherein like numbers reference like
elements.
[0042] FIG. 1 is a schematic configuration diagram illustrating a
projector according to a first embodiment.
[0043] FIG. 2 is a sectional view illustrating a configuration of a
light source apparatus according to the first embodiment.
[0044] FIG. 3 is a partially enlarged sectional view of a discharge
lamp according to the first embodiment.
[0045] FIG. 4 is a circuit diagram illustrating a discharge lamp
lighting device and a control device according to the first
embodiment.
[0046] FIG. 5 is a block diagram illustrating a configuration
example of the control device according to the first
embodiment.
[0047] FIG. 6 is a block diagram illustrating various constituent
elements of the projector according to the first embodiment.
[0048] FIG. 7A is a diagram illustrating states of protrusions of
electrode tips of the discharge lamp.
[0049] FIG. 7B is a diagram illustrating states of protrusions of
electrode tips of the discharge lamp.
[0050] FIG. 7C is a timing chart illustrating a relationship
between a driving current supplied to the discharge lamp and the
temperature of an electrode.
[0051] FIG. 8 is a diagram illustrating an example of a driving
current waveform according to the first embodiment.
[0052] FIG. 9 is a graph illustrating temperature changes of a
second electrode and a discharge lamp main body according to the
first embodiment.
[0053] FIG. 10 is a diagram illustrating an example of a driving
current waveform according to a second embodiment.
[0054] FIG. 11 is a diagram illustrating an example of a driving
current waveform according to a third embodiment.
[0055] FIG. 12 is a diagram for explaining a mercury bridge.
[0056] FIG. 13 is a diagram for explaining a mercury bridge.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0057] Hereinafter, with reference to the drawings, a projector
according to embodiments of the invention will be described.
[0058] The scope of the invention is not limited to the following
embodiments, and can be arbitrarily changed within the scope of the
technical spirit of the invention. In the following drawings, for
better understanding of each constituent element, a scale, the
number, and the like thereof in each structure may be different
from a scale, the number, and the like thereof in an actual
structure.
First Embodiment
[0059] As illustrated in FIG. 1, a projector 500 of the present
embodiment includes a light source apparatus 200, a collimating
lens 305, an illumination optical system 310, a color separation
optical system 320, three liquid crystal light valves (light
modulation devices) 330R, 330G and 330B, a cross dichroic prism
340, and a projection optical system 350.
[0060] Light emitted from the light source apparatus 200 passes
through the collimating lens 305 and is incident to the
illumination optical system 310. The collimating lens 305
collimates the light from the light source apparatus 200.
[0061] The illumination optical system 310 adjusts the illuminance
of the light emitted from the light source apparatus 200 so that
the illuminance is uniformized on the liquid crystal light valves
330R, 330G and 330B. The illumination optical system 310 aligns
polarization directions of the light emitted from the light source
apparatus 200 in one direction. This is aimed at effectively using
the light emitted from the light source apparatus 200 in the liquid
crystal light valves 330R, 330G and 330B.
[0062] The light having undergone the adjustment of the illuminance
distribution and the polarization directions is incident to the
color separation optical system 320. The color separation optical
system 320 separates the incident light into three color light
beams including red light (R), green light (G), and blue light (B).
The three color light beams are respectively modulated according to
video signals by the liquid crystal light valves 330R, 330G and
330B which correspond to the respective color light beams. The
liquid crystal light valves 330R, 330G and 330B respectively
include liquid crystal panels 560R, 560G and 560B which will be
described later, and polarization plates (not illustrated). The
polarization plates are disposed on a light incidence side and a
light emission side of each of the liquid crystal panels 560R, 560G
and 560B.
[0063] The three modulated color light beams are combined with each
other by the cross dichroic prism 340. The combined light is
incident to the projection optical system 350. The projection
optical system 350 projects the incident light onto a screen 700
(refer to FIG. 6). Thus, a video is displayed on the screen 700. In
addition, well-known configurations may be employed as
configurations of the collimating lens 305, the illumination
optical system 310, the color separation optical system 320, the
cross dichroic prism 340, and the projection optical system
350.
[0064] The light source apparatus 200 includes a light source unit
210, a discharge lamp lighting device 10, a control device
(controller) 40, an input reception unit 45, and a cooling device
(cooling unit) 50.
[0065] FIG. 2 is a sectional view illustrating a configuration of
the light source apparatus 200. FIG. 2 shows a sectional view of
the light source unit 210. In FIG. 2, the control device 40 and the
cooling device 50 are not illustrated.
Light Source Unit
[0066] As illustrated in FIG. 2, the light source unit 210 includes
a discharge lamp 90, a main reflection mirror (reflection mirror)
112, and a subsidiary reflection mirror 113.
[0067] The discharge lamp lighting device 10 supplies a driving
current I to the discharge lamp 90 so as to light the discharge
lamp 90. The main reflection mirror 112 reflects light emitted from
the discharge lamp 90 in an irradiation direction (predetermined
direction) D. The irradiation direction D is parallel to an optical
axis AX of the discharge lamp 90.
[0068] The discharge lamp 90 includes a discharge lamp main body
510, a first electrode 92, and a second electrode 93.
[0069] The discharge lamp main body 510 has a rod shape extending
in the irradiation direction D. One end of the discharge lamp main
body 510, that is, one end of the discharge lamp 90 is referred to
as a first end 90e1. The other end of the discharge lamp main body
510, that is, the other end of the discharge lamp 90 is referred to
as a second end 90e2. A material of the discharge lamp main body
510 is, for example, a light transmissive material such as quartz
glass. A central portion of the discharge lamp main body 510 is
swollen in a spherical shape, and the inside thereof is a discharge
space 91. A gas which is a discharge medium containing mercury,
rare gases, metal halogen compounds, and the like is enclosed in
the discharge space 91.
[0070] Tips of the first electrode 92 and the second electrode 93
protrude in the discharge space 91. The first electrode 92 is
disposed on the first end 90e1 side of the discharge space 91. The
second electrode 93 is disposed on the second end 90e2 side of the
discharge space 91. Each of the first electrode 92 and the second
electrode 93 has a rod shape extending in the optical axis AX. The
tips of the first electrode 92 and the second electrode 93 are
disposed to face each other with a predetermined distance in the
discharge space 91. A material of each of the first electrode 92
and the second electrode 93 is, for example, a metal such as
tungsten.
[0071] FIG. 3 is an enlarged sectional view illustrating a part of
the discharge lamp 90.
[0072] As illustrated in FIG. 3, the first electrode 92 includes a
core rod 533, a coil portion 532, a main body portion 531, and a
protrusion 531p. The first electrode 92 is formed by winding a wire
material as an electrode material (tungsten or the like) on the
core rod 533 in a stage of being enclosed in the discharge lamp
main body 510 so as to form the coil portion 532 and by heating and
melting the formed coil portion 532. Consequently, the main body
portion 531 having a large thermal capacity and the protrusion 531p
where an arc AR is generated are formed on a tip side of the first
electrode 92.
[0073] The second electrode 93 includes a core rod 543, a coil
portion 542, a main body portion 541, and a protrusion 541p. The
second electrode 93 is formed in the same manner as the first
electrode 92.
[0074] The first electrode 92 and the second electrode 93 have the
same configuration, and, thus, in the following description, only
the first electrode 92 will be described as a representative in
some cases. The protrusion 531p of the first electrode 92 and the
protrusion 541p of the second electrode 93 have the same
configuration, and, thus, in the following description, only the
protrusion 531p will be described as a representative in some
cases.
[0075] As illustrated in FIG. 2, a first terminal 536 is provided
at the first end 90e1 of the discharge lamp 90. The first terminal
536 and the first electrode 92 are electrically connected to each
other via a conductive member 534 which penetrates through the
discharge lamp 90. Similarly, a second terminal 546 is provided at
the second end 90e2 of the discharge lamp 90. The second terminal
546 and the second electrode 93 are electrically connected to each
other via a conductive member 544 which penetrates through the
discharge lamp 90. A material of each of the first terminal 536 and
the second terminal 546 is, for example, a metal such as tungsten.
As a material of each of the conductive members 534 and 544, for
example, a molybdenum foil is used.
[0076] The first terminal 536 and the second terminal 546 are
connected to the discharge lamp lighting device 10. The discharge
lamp lighting device 10 supplies the driving power for driving the
discharge lamp 90 to the first terminal 536 and the second terminal
546. As a result, arc discharge occurs between the first electrode
92 and the second electrode 93. Light (discharge light) occurring
due to the arc discharge is radiated in all directions from the
discharge position as indicated by dashed arrows.
[0077] As illustrated in FIG. 3, if the discharge lamp 90 is
lighted, a gas enclosed in the discharge space 91 is heated due to
generation of the arc AR and undergoes convection in the discharge
space 91. Specifically, since the temperature of the arc AR and a
region therearound is considerably high, convections AF (indicated
by a dot chain arrow in FIG. 3) which flow vertically upward from
the arc AR are formed in the discharge space 91. The convections AF
come into contact with the inner wall of the discharge lamp main
body 510, move along the inner wall of the discharge lamp main body
510, and descend while being cooled as a result of passing through
the core rods 533 and 543 of the first electrode 92 and the second
electrode 93.
[0078] The descending convections AF further descend along the
inner wall of the discharge lamp main body 510, but come into
contact with each other on a vertically lower side of the arc AR,
and thus ascend so as to return to the upper arc AR. As a result of
the convections AF moving along the inner wall of the discharge
lamp main body 510, the discharge lamp main body 510 is heated.
[0079] As illustrated in FIG. 2, the main reflection mirror 112 is
fixed to the first end 90e1 of the discharge lamp 90 via a fixation
member 114. The main reflection mirror 112 reflects light which
travels toward an opposite side to the irradiation direction D
among discharge light beams, in the irradiation direction D. A
shape of a reflection surface (a surface on the discharge lamp 90
side) of the main reflection mirror 112 is not particularly limited
within a range in which discharge light can be reflected in the
irradiation direction D, and may be, for example, a spheroidal
shape or a rotating parabolic shape. For example, in a case where a
shape of the reflection surface of the main reflection mirror 112
is a rotating parabolic shape, the main reflection mirror 112 can
convert discharge light into light which is substantially parallel
to the optical axis AX. Consequently, the collimating lens 305 can
be omitted.
[0080] The subsidiary reflection mirror 113 is fixed to the second
end 90e2 side of the discharge lamp 90 via a fixation member 522. A
shape of a reflection surface (a surface on the discharge lamp 90
side) of the subsidiary reflection mirror 113 is a spherical shape
which surrounds a portion of the discharge space 91 on the second
end 90e2 side. The subsidiary reflection mirror 113 reflects light
which travels toward an opposite side to the side on which the main
reflection mirror 112 is disposed among the discharge light beams,
toward the main reflection mirror 112. Consequently, it is possible
to increase usage efficiency of the light radiated from the
discharge space 91.
[0081] A material of each of the fixation members 114 and 522 is
not particularly limited as long as the material is a heat
resistant material which can resist heat generated from the
discharge lamp 90, and is, for example, an inorganic adhesive.
Discharge Lamp Lighting Device
[0082] FIG. 4 is a diagram illustrating an example of a circuit
configuration of the discharge lamp lighting device 10 and the
control device 40.
[0083] As illustrated in FIG. 4, the discharge lamp lighting device
10 includes a power control circuit 20, a polarity inversion
circuit 30, an operation detection unit 60, and an igniter circuit
70.
[0084] The power control circuit 20 generates the driving power
which is supplied to the discharge lamp 90. In the present
embodiment, the power control circuit 20 is constituted of a down
chopper circuit which receives a voltage from a DC power source
device 80 and outputs a DC current Id by stepping down the input
voltage.
[0085] The power control circuit 20 is configured to include a
switch element 21, a diode 22, a coil 23, and a capacitor 24. The
switch element 21 is constituted of, for example, a transistor. In
the present embodiment, one end of the switch element 21 is
connected to a positive voltage side of the DC power source device
80, and the other end thereof is connected to a cathode terminal of
the diode 22 and one end of the coil 23.
[0086] One end of the capacitor 24 is connected to the other end of
the coil 23, and the other end of the capacitor 24 is connected to
an anode terminal of the diode 22 and a negative voltage side of
the DC power source device 80. A current control signal is input to
a control terminal of the switch element 21 from the control device
40, and thus turning-on and turning-off of the switch element 21
are controlled. As the current control signal, for example, a pulse
width modulation (PWM) control signal may be used.
[0087] If the switch element 21 is turned on, a current flows
through the coil 23, and thus energy is accumulated in the coil 23.
Thereafter, if the switch element 21 is turned off, the energy
accumulated in the coil 23 is released along a path passing through
the capacitor 24 and the diode 22. As a result, the DC current Id
is generated which is proportional to a time period in which the
switch element 21 is turned on.
[0088] The polarity inversion circuit 30 inverts a polarity of the
DC current Id which is input from the power control circuit 20, at
a predetermined timing. Consequently, the polarity inversion
circuit 30 generates and outputs a driving current I as a DC which
is continuously maintained only for a controlled time period, or a
driving current I as an AC which has any frequency. In the present
embodiment, the polarity inversion circuit 30 is constituted of an
inverter bridge circuit (full bridge circuit).
[0089] The polarity inversion circuit 30 includes, for example, a
first switch element 31, a second switch element 32, a third switch
element 33, and a fourth switch element 34, constituted of
transistors. The polarity inversion circuit 30 has a configuration
in which the first switch element 31 and the second switch element
32 which are connected in series to each other are connected in
parallel to the third switch element 33 and the fourth switch
element 34 which are connected in series to each other. A polarity
inversion control signal is input from the control device 40 to
each of control terminals of the first switch element 31, the
second switch element 32, the third switch element 33, and the
fourth switch element 34. Turning-on and turning-off operations of
each of the first switch element 31, the second switch element 32,
the third switch element 33, and the fourth switch element 34 are
controlled on the basis of the polarity inversion control
signal.
[0090] In the polarity inversion circuit 30, an operation is
repeatedly performed in which the first switch element 31 and the
fourth switch element 34, and the second switch element 32 and the
third switch element 33 are alternately turned on or off.
Therefore, the polarities of the DC current Id output from the
power control circuit 20 are alternately inverted. The polarity
inversion circuit 30 generates and outputs a driving current I as a
DC which is continuously maintained in the same polarity state only
for a controlled time period or a driving current I as an AC having
a controlled frequency, from a common connection point between the
first switch element 31 and the second switch element 32, and a
common connection point between the third switch element 33 and the
fourth switch element 34.
[0091] In other words, in the polarity inversion circuit 30, the
second switch element 32 and the third switch element 33 are
controlled to be turned off when the first switch element 31 and
the fourth switch element 34 are turned on, and the second switch
element 32 and the third switch element 33 are controlled to be
turned on when the first switch element 31 and the fourth switch
element 34 are turned off. Thus, the driving current I is generated
which flows in order of the first switch element 31, the discharge
lamp 90, and the fourth switch element 34 from one end of the
capacitor 24 when the first switch element 31 and the fourth switch
element 34 are turned on. The driving current I is generated which
flows in order of the third switch element 33, the discharge lamp
90, and the second switch element 32 from one end of the capacitor
24 when the second switch element 32 and the third switch element
33 are turned on.
[0092] In the present embodiment, the portion including the power
control circuit 20 and the polarity inversion circuit 30
corresponds to a discharge lamp driving unit 230. In other words,
the discharge lamp driving unit 230 supplies the driving current I
for driving the discharge lamp 90 to the discharge lamp 90.
[0093] The operation detection unit 60 includes a voltage detection
portion which detects a lamp voltage of the discharge lamp 90 and
outputs lamp voltage information to the control device 40. The
operation detection unit 60 includes a current detection portion or
the like which detects the driving current I and outputs driving
current information to the control device 40. In the present
embodiment, the operation detection unit 60 is configured to
include a first resistor 61, a second resistor 62, and a third
resistor 63.
[0094] In the present embodiment, the voltage detection portion of
the operation detection unit 60 detects the lamp voltage on the
basis of a voltage divided by the first resistor 61 and the second
resistor 62 which are connected in parallel to the discharge lamp
90 and are connected in series to each other. In addition, in the
present embodiment, the current detection portion detects the
driving current I on the basis of a voltage occurring at the third
resistor 63 which is connected in series to the discharge lamp
90.
[0095] The igniter circuit 70 operates only at the time of starting
of lighting of the discharge lamp 90. The igniter circuit 70
supplies a high voltage (a voltage higher than at normal lighting
of the discharge lamp 90) which is necessary to cause dielectric
breakdown between the electrodes (between the first electrode 92
and the second electrode 93) of the discharge lamp 90 and thus to
form a discharge path, between the electrodes of the discharge lamp
90 (between the first electrode 92 and the second electrode 93) at
the time of starting of lighting of the discharge lamp 90. In the
present embodiment, the igniter circuit 70 is connected in parallel
to the discharge lamp 90.
Control Device
[0096] The control device 40 controls various operations from
starting to stoppage of operations of the projector 500. The
control device 40 controls the discharge lamp driving unit 230
according to a driving current waveform of the driving current I.
In the example illustrated in FIG. 4, the control device 40
controls the power control circuit 20 and the polarity inversion
circuit 30 so as to control parameters such as duration in which
the driving current I is continuously maintained to have the same
polarity, and a current value and a frequency of the driving
current I. The control device 40 performs polarity inversion
control for controlling the duration in which the driving current I
is continuously maintained to have the same polarity, a frequency
of the driving current I, and the like, on the polarity inversion
circuit 30, on the basis of a polarity inversion timing. The
control device 40 performs current control for controlling a
current value of the output DC current Id on the power control
circuit 20.
[0097] The control device 40 controls the discharge lamp driving
unit 230 so as to cause a period in which an alternating current of
the driving current I is supplied to the discharge lamp 90 to
transition from a steady lighting period (first AC period) PH1 to a
heating period (second AC period) PH21 when the input reception
unit 45 receives a stop operation on the projector 500, that is, a
putting-out operation on the discharge lamp 90. Details thereof
will be described later.
[0098] In the present embodiment, the control device 40 controls
the cooling device 50. The control device 40 drives the cooling
device 50 with a fan voltage (second output) which is higher than a
steady fan voltage (first output) in the heating period PH21 which
will be described later. Details thereof will be described
later.
[0099] A configuration of the control device 40 is not particularly
limited. In the present embodiment, the control device 40 is
configured to include a system controller 41, a power control
circuit controller 42, and a polarity inversion circuit controller
43. Some or all of the controllers of the control device 40 may be
configured by using semiconductor integrated circuits.
[0100] The system controller 41 controls the power control circuit
controller 42 and the polarity inversion circuit controller 43 so
as to control the power control circuit 20 and the polarity
inversion circuit 30. The system controller 41 may control the
power control circuit controller 42 and the polarity inversion
circuit controller 43 on the basis of a lamp voltage and the
driving current I detected by the operation detection unit 60.
[0101] In the present embodiment, the system controller 41 is
connected to a storage unit 44.
[0102] The system controller 41 may control the power control
circuit 20 and the polarity inversion circuit 30 on the basis of
information stored in the storage unit 44. The storage unit 44 may
store, for example, information regarding driving parameters such
as the duration in which the driving current I is continuously
maintained to have the same polarity, a current value, a frequency,
a waveform, and a modulation pattern of the driving current I.
[0103] The power control circuit controller 42 outputs a current
control signal to the power control circuit 20 on the basis of a
control signal from the system controller 41, so as to control the
power control circuit 20.
[0104] The polarity inversion circuit controller 43 outputs a
polarity inversion control signal to the polarity inversion circuit
30 on the basis of a control signal from the system controller 41,
so as to control the polarity inversion circuit 30.
[0105] The control device 40 may be implemented by using a
dedicated circuit so as to perform the above-described control or
various control operations related to processes to be described
later. In contrast, the control device 40 may function as a
computer, for example, by executing a control program stored in the
storage unit 44, so as to perform various control operations
related to such processes.
[0106] FIG. 5 is a diagram illustrating another configuration
example of the control device 40. As illustrated in FIG. 5, the
control device 40 may be configured to function as a current
controller 40-1 which controls the power control circuit 20 and a
polarity inversion controller 40-2 which controls the polarity
inversion circuit 30 according to the control program.
Input Reception Unit
[0107] The input reception unit 45 illustrated in FIG. 1 receives a
predetermined operation from a user. The input reception unit 45
receives user's operations, such as turning-on and turning-off of
the supply of power to the projector 500, or changing of lighting
modes. In the present embodiment, the input reception unit 45 is
connected to the control device 40. In a case where a user's
operation is received, the input reception unit 45 outputs an
operation signal corresponding to the operation to the control
device 40.
[0108] A method of the input reception unit 45 receiving an
operation is not particularly limited. For example, the input
reception unit 45 may receive an operation performed by pressing
various buttons attached to a casing of the projector 500, and may
receive an operation on the basis of a signal sent from a remote
controller of the projector 500.
[0109] In the present embodiment, an operation of turning off the
supply of power to the projector 500, that is, a stop operation
includes a first stop operation and a second stop operation. In
other words, in the present embodiment, a user performs the first
stop operation and the second stop operation so as to turn off the
supply of power to the projector 500. As an example, the user may
turn off the supply of power to the projector 500 by pressing a
power button attached to the casing of the projector 500 twice.
[0110] If the input reception unit 45 receives the first stop
operation, the control device 40 performs a checking operation for
checking whether or not turning-off of the supply of power to the
projector 500 is necessary. In other words, in a case where the
input reception unit 45 receives the first stop operation, the
control device 40 performs a checking operation for checking
whether or not the supply stoppage of the driving current I to the
discharge lamp 90 is necessary.
[0111] The checking operation is not particularly limited, and any
method may be used as long as the method is allowed the user to
check operation stoppage of the projector 500. As a checking
operation, for example, a method may be selected in which an image
for checking operation stoppage of the projector 500 is displayed
on the screen 700. As a checking operation, a method may be
selected in which sound for checking operation stoppage of the
projector 500 is output.
[0112] The second stop operation is an operation which is performed
temporally later than the first stop operation. The user performs
the first stop operation, and then performs the second stop
operation in a case of deciding execution of operation stoppage of
the projector 500 in a checking operation. If the input reception
unit 45 receives the second stop operation, the control device 40
controls the discharge lamp driving unit 230 to stop the supply of
the driving current I to the discharge lamp 90. Consequently, the
supply of power to the projector 500 is turned off.
[0113] The input reception unit 45 may receive the first stop
operation and the second stop operation in the same method, or in
different methods.
Cooling Device
[0114] The cooling device 50 includes, for example, a fan. The fan
of the cooling device 50 is constituted of, for example, a sirocco
fan. The fan of the cooling device 50 sucks cooled air in the
casing of the projector 500 and sends the air to the light source
unit 210. The cooling device 50 can cool the discharge lamp 90 of
the light source unit 210 and the main reflection mirror 112 of the
light source unit 210.
[0115] In the present embodiment, the cooling device 50 may include
a single fan which can send air to the discharge lamp 90 and the
main reflection mirror 112, and may include a fan which can send
air to the discharge lamp 90 and a fan which can send air to the
main reflection mirror 112.
[0116] Hereinafter, a circuit configuration of the projector 500
will be described.
[0117] FIG. 6 is a diagram illustrating an example of a circuit
configuration of the projector 500 according to the present
embodiment. The projector 500 includes, as illustrated in FIG. 6,
an image signal conversion unit 501, the DC power source device 80,
the liquid crystal panels 560R, 560G and 560B, and an image
processing device 570, in addition to the configuration illustrated
in FIG. 1.
[0118] The image signal conversion unit 501 converts image signals
502 (luminance-color difference signals, analog RGB signals, or the
like) which are input from an external device into digital RGB
signals with a predetermined word length so as to generate image
signals 512R, 512G and 512B which are then supplied to the image
processing device 570.
[0119] The image processing device 570 performs an image process on
each of the three image signals 512R, 512G and 512B. The image
processing device 570 supplies driving signals 572R, 572G and 572B
for respectively driving the liquid crystal panels 560R, 560G and
560B, to the liquid crystal panels 560R, 560G and 560B.
[0120] The DC power source device 80 converts an AC voltage
supplied from an external AC power source 600 into a constant DC
voltage. The DC power source device 80 supplies DC voltages to the
image signal conversion unit 501 and the image processing device
570 located on a secondary side of a transformer (not illustrated
but included in the DC power source device 80) and the discharge
lamp lighting device 10 located on a primary side of the
transformer.
[0121] The discharge lamp lighting device 10 generates a high
voltage between the electrodes of the discharge lamp 90 so as to
cause dielectric breakdown and thus to form a discharge path during
activation. Thereafter, the discharge lamp lighting device 10
supplies driving current I for the discharge lamp 90 maintaining
discharge.
[0122] The liquid crystal panels 560R, 560G and 560B are
respectively provided in the above-described liquid crystal light
valves 330R, 330G and 330B. The liquid crystal panels 560R, 560G
and 560B modulate transmittance (luminance) of the color light
beams which are respectively incident to the liquid crystal panels
560R, 560G and 560B via the above-described optical systems on the
basis of the respective driving signals 572R, 572G and 572B.
[0123] Hereinafter, a description will be made of a relationship
between a polarity of the driving current I and the temperature of
the electrode.
[0124] FIGS. 7A to 7C are diagrams for explaining a relationship
between a polarity of the driving current I supplied to the
discharge lamp 90 and the temperature of the electrode. FIGS. 7A
and 7B illustrate operation states of the first electrode 92 and
the second electrode 93.
[0125] FIGS. 7A and 7B illustrate the tips of the first electrode
92 and the second electrode 93. Discharge occurring between the
first electrode 92 and the second electrode 93 mainly occurs
between the protrusion 531p and the protrusion 541p. In a case
where the protrusions 531p and 541p are provided as in the present
embodiment, movements of discharge positions (arc positions) at the
first electrode 92 and the second electrode 93 can be minimized
compared with a case where no protrusions are provided.
[0126] FIG. 7A illustrates a first polarity state in which the
first electrode 92 operates as an anode, and the second electrode
93 operates as a cathode. In the first polarity state, electrons
move from the second electrode 93 (cathode) to the first electrode
92 (anode) due to discharge. The electrons are emitted from the
cathode (second electrode 93). The electrons emitted from the
cathode (second electrode 93) collide with the tip (protrusion
531p) of the anode (first electrode 92). Heat is generated due to
the collision, and thus the temperature of the first electrode 92
increases.
[0127] FIG. 7B illustrates a second polarity state in which the
first electrode 92 operates as a cathode, and the second electrode
93 operates as an anode. Contrary to the first polarity state, in
the second polarity state, electrons move from the first electrode
92 to the second electrode 93. As a result, the temperature of the
tip of the second electrode 93 increases.
[0128] As mentioned above, when the driving current I is supplied
to the discharge lamp 90, the temperature of the anode with which
the electrons collide increases. On the other hand, the temperature
of the cathode which emits the electrons decreases during emission
of the electrons toward the anode.
[0129] An inter-electrode distance L between the first electrode 92
and the second electrode 93 is a distance between the protrusion
531p and the protrusion 541p. During driving of the discharge lamp
90, the protrusion 531p repeatedly performs melting and growth
according to increase and decrease in the temperature of the first
electrode 92. This is also the same for the protrusion 541p. The
inter-electrode distance L increases when the protrusions 531p and
541p are melted, and decreases when the protrusions grow.
[0130] An upper part of FIG. 7C shows a timing chart illustrating
an example of the driving current I supplied to the discharge lamp
90. On the upper part of FIG. 7C, a transverse axis expresses time
T, and a longitudinal axis expresses a current value of the driving
current I. The driving current I indicates a current which flows
through the discharge lamp 90. A positive value indicates the first
polarity state, and a negative value indicates the second polarity
state. The upper part of FIG. 7C illustrates the driving current I
in the steady lighting period PH1.
[0131] In the present embodiment, a square wave alternating current
is used as the driving current I as illustrated on the upper part
of FIG. 7C. In the steady lighting period PH1, the driving current
I is supplied to the discharge lamp 90 so that a first polarity
period P1 in which the first polarity state occurs and a second
polarity period P2 in which the second polarity state occurs are
alternately repeated.
[0132] In the example illustrated on the upper part of FIG. 7C, an
average current value in the first polarity period P1 is Im1, and
an average current value in the second polarity period P2 is -Im1.
A driving frequency of the driving current I appropriate for
driving of the discharge lamp 90 may be determined experimentally
in accordance with characteristics of the discharge lamp 90.
[0133] A lower part of FIG. 7C shows a timing chart illustrating a
temperature change of the first electrode 92. A transverse axis
expresses time T, and a longitudinal axis expresses the temperature
H. The temperature H of the first electrode 92 increases in the
first polarity period P1, and the temperature H of the first
electrode 92 decreases in the second polarity period P2. The first
polarity period P1 and the second polarity period P2 are repeated,
and thus the temperature H periodically changes between the minimum
value Hmin and the maximum value Hmax. Although not illustrated,
the temperature of the second electrode 93 changes in an opposite
phase to the phase of the temperature H of the first electrode 92.
In other words, the temperature of the second electrode 93
decreases in the first polarity period P1, and the temperature of
the second electrode 93 increases in the second polarity period
P2.
[0134] Next, a description will be made of control on the cooling
device 50, performed by the control device 40.
[0135] The cooling device 50 can execute a steady output mode and a
high output mode. The output mode of the cooling device 50 is
controlled by the control device 40.
[0136] The steady output mode is an output mode in which a steady
fan voltage (first output) is applied to the fan of the cooling
device 50. The steady fan voltage is a fan voltage which is set in
order to maintain the temperature of the discharge lamp 90 to be an
appropriate temperature, and is set according to driving power. In
the present embodiment, the steady fan voltage is set to be
proportional to, for example, the driving power.
[0137] In the present specification, a fan voltage (steady fan
voltage) is being proportional to driving power includes not only a
case where the fan voltage is accurately proportional to the
driving power but also, for example, a case where errors ranging
from about 0.9 times to 1.1 times are allowable.
[0138] The high output mode is an output mode in which a fan
voltage (second output) which is higher than the steady fan voltage
(first output) is applied to the fan of the cooling device 50 with
respect to driving power. In other words, in the present
embodiment, the second output is a fan voltage which causes the
temperature of the discharge lamp 90 to become lower than an
appropriate temperature when the discharge lamp 90 is driven with
driving power.
[0139] In the present embodiment, the controller 40 drives the
cooling device 50 in the steady output mode in the steady lighting
period PH1. In the present embodiment, the control device 40 drives
the cooling device 50 in the high output mode in at least a part of
the heating period PH21.
[0140] For example, in a case where the cooling device 50 is
configured to include a fan which can send air to the discharge
lamp 90 and a fan which can send air to the main reflection mirror
112, either one of the fan which can send air to the discharge lamp
90 and the fan which can send air to the main reflection mirror 112
can be driven in the high output mode.
[0141] Next, a description will be made of the driving current I
supplied to the discharge lamp 90 in the present embodiment.
[0142] FIG. 8 is a diagram illustrating an example of a driving
current waveform DW1 of the present embodiment. FIG. 8 illustrates
the driving current waveform DW1 before and after the input
reception unit 45 receives a stop operation.
[0143] As illustrated in FIG. 8, the driving current waveform DW1
(driving current I) includes the steady lighting period PH1 and the
heating period PH21 in which an alternating current is supplied to
the discharge lamp 90. In the present embodiment, the driving
current waveform DW1 transitions from the steady lighting period
PH1 to the heating period PH21 when the input reception unit 45
receives the first stop operation.
[0144] The steady lighting period PH1 alternately includes the
first polarity period P1 and the second polarity period P2 as
described above.
[0145] In the present embodiment, the heating period PH21 is
entirely provided after the input reception unit 45 receives the
first stop operation until receiving the second stop operation. In
other words, a length t1 of the heating period PH21 corresponds to
a time period after the user performs the first stop operation
until performing the second stop operation.
[0146] The heating period PH21 alternately includes a first
polarity period P11 in which the first polarity state occurs and a
second polarity period P21 in which the second polarity state
occurs. In other words, in the heating period PH21, an alternating
current is supplied to the discharge lamp 90.
[0147] In the present embodiment, a value of the driving current I
of the first polarity period P11 is, for example, Im1. In other
words, the value of the driving current I of the first polarity
period P11 is the same as, for example, a value of the driving
current I of the first polarity period P1 in the steady lighting
period PH1.
[0148] A value of the driving current I of the second polarity
period P21 is, for example, -Im2. An absolute value of -Im2 is
greater than an absolute value of -Im1. In other words, an absolute
value of the driving current I of the second polarity period P21 in
the heating period PH21 is greater than an absolute value of the
driving current I of the second polarity period P2 in the steady
lighting period PH1.
[0149] As an example, an absolute value of the driving current I of
the second polarity period P21 in the heating period PH21 is 0.8
times or greater and 1.25 times or smaller than an absolute value
of the driving current I obtained when rating power is supplied to
the discharge lamp 90. In other words, driving power of the second
polarity period P21 in the heating period PH21 is 0.8 times or
higher and 1.25 times or lower than the rating power. The absolute
value of the driving current I of the second polarity period P21 is
set in the above-described way, and thus it is possible to
appropriately increase the temperature of the second electrode 93
and also to prevent the second electrode 93 from being
depleted.
[0150] In the example illustrated in FIG. 8, a frequency of the
driving current I in the heating period PH21 is the same as a
frequency in the steady lighting period PH1. A length tp of the
first polarity period P1 in the steady lighting period PH1 is the
same as a length tp1 of the first polarity period P11 in the
heating period PH21. A length to of the second polarity period P2
in the steady lighting period PH1 is the same as a length tn1 of
the second polarity period P21 in the heating period PH21.
[0151] The control device 40 controls the discharge lamp driving
unit 230 according to the above-described driving current waveform
DW1.
[0152] The above-described embodiment may be expressed as a control
method for the projector. In other words, a control method for the
projector of the present embodiment includes causing the discharge
lamp 90 to emit light; causing the main reflection mirror 112 to
reflect the light emitted from the discharge lamp 90 in the
irradiation direction D; and causing the input reception unit 45 to
receive a predetermined operation, in which the discharge lamp 90
includes the discharge lamp main body 510 having the discharge
space 91 therein, and the first electrode 92 and the second
electrode 93 protruding in the discharge space 91, in which the
main reflection mirror 112 is attached to the first end 90e1 of the
discharge lamp main body 510, the first electrode 92 is disposed on
the first end 90e1 side, and the second electrode 93 is disposed on
the second end 90e2 side of the discharge lamp main body 510 on an
opposite side to the first end 90e1, in which the driving current I
includes the steady lighting period PH1 and the heating period PH21
in which an alternating current is supplied to the discharge lamp
90, in which the steady lighting period PH1 and the heating period
PH21 alternately include the first polarity periods P1 and P11 in
which the first electrode 92 serves as an anode and the second
polarity periods P2 and P21 in which the second electrode 93 serves
as the anode, in which, in a case where the input reception unit 45
receives a stop operation on the projector, a period in which an
alternating current is supplied to the discharge lamp 90
transitions from the steady lighting period PH1 to the heating
period PH21, and in which an absolute value of the driving current
I of the second polarity period P21 in the heating period PH21
becomes greater than an absolute value of the driving current I of
the second polarity period P2 in the steady lighting period
PH1.
[0153] According to the present embodiment, it is possible to
provide the projector having a configuration capable of minimizing
a mercury bridge and of minimizing deterioration in convenience.
Hereinafter, details thereof will be described.
[0154] First, the mercury bridge will be described.
[0155] FIGS. 12 and 13 are diagrams for explaining the mercury
bridge. FIG. 12 illustrates a state in which time does not elapse
much after the discharge lamp 90 is put out. FIG. 13 illustrates a
state in which time elapses to some extent after the discharge lamp
90 is put out, and thus the mercury bridge is generated.
[0156] As illustrated in FIG. 12, if the discharge lamp 90 is put
out, the temperatures of the first electrode 92 and the second
electrode 93, and the temperature of the discharge lamp main body
510 decrease. For this reason, gaseous mercury Hg enclosed in the
discharge space 91 condenses. The temperature of the discharge lamp
main body 510 is lower than the temperatures of the first electrode
92 and the second electrode 93, and thus mercury Hg condenses on
the inner wall of the discharge lamp main body 510. Mercury Hg very
easily condenses at an end of the inner wall of the discharge lamp
main body 510 on the side where the first electrode 92 protrudes
and at an end thereof on the side where the second electrode 93
protrudes. This is because the end of the inner wall of the
discharge lamp main body 510 on the side where the first electrode
92 protrudes and at the end of the inner wall of the discharge lamp
main body 510 on the side where the second electrode 93 protrudes
are separated from the location where the arc discharge occurs, and
thus the temperatures thereof are more easily become lower than the
temperatures of other portions of the inner wall of the discharge
lamp main body 510.
[0157] As illustrated in FIG. 13, if time elapses to some extent
after the discharge lamp 90 is put out, a part of mercury Hg may be
vaporized again. This is because the pressure in the discharge
space 91 is reduced due to condensation of mercury Hg, and thus the
boiling point of mercury Hg is reduced.
[0158] Here, the main reflection mirror 112 is attached on the
first end 90e1 side of the discharge lamp 90. Since the main
reflection mirror 112 has a relatively large thermal capacity, the
temperature thereof is easily maintained. Consequently, heat of the
main reflection mirror 112 is transferred to the first end 90e1,
and thus the temperature on the first end 90e1 side of the
discharge lamp main body 510 is unlikely to become lower than the
temperature on the second end 90e2 side of the discharge lamp main
body 510. Therefore, the temperature on the first end 90e1 side of
the inner wall of the discharge lamp main body 510 is likely to
become higher than the boiling point of mercury Hg, and mercury Hg
which has condensed on the first end 90e1 side of the inner wall of
the discharge lamp main body 510 is easily vaporized.
[0159] Vaporized mercury Hg condenses again at a location whose
temperature is lower than the boiling point of mercury Hg in the
discharge space 91. The temperatures of the first electrode 92 and
the second electrode 93 more easily decrease than the temperature
of the discharge lamp main body 510. For this reason, the
temperatures of the first electrode 92 and the second electrode 93
become lower than the temperature of the discharge lamp main body
510 if some time elapses after the discharge lamp 90 is put out. At
this time, since the first electrode 92 is provided on the first
end 90e1 side and thus receives heat transferred from the main
reflection mirror 112, the temperature thereof is likely to be
maintained. In other words, the temperature of the first electrode
92 is unlikely to become lower than the temperature of the second
electrode 93. Therefore, the temperature of the second electrode 93
is likely to become lower than the temperature of the discharge
lamp main body 510 and the boiling point of mercury Hg earlier than
the temperature of the first electrode 92.
[0160] FIG. 9 is a graph illustrating a temperature change of the
second electrode 93 and a temperature change of the discharge lamp
main body 510. In FIG. 9, a transverse axis expresses time T, and a
longitudinal axis expresses a temperature H. In FIG. 9, a solid
line indicates a temperature Hp1 of the second electrode 93 of the
present embodiment. In FIG. 9, a dashed line indicates a
temperature Hp2 of the second electrode 93 in a comparative
example. In FIG. 9, a dot chain line indicates a temperature H1a of
the discharge lamp main body 510.
[0161] The comparative example refers to a case where, when the
input reception unit 45 receives a stop operation on the projector
500, the discharge lamp 90 is put out without transition of a
period in which an alternating current is supplied to the discharge
lamp 90 from the steady lighting period PH1 to the heating period
PH21.
[0162] The temperature H1a of the discharge lamp main body 510 is
the temperature of a portion whose temperature is lowest on the
inner wall of the discharge lamp main body 510.
[0163] As illustrated in FIG. 9, at the time when the discharge
lamp 90 is put out, the temperature H1a of the discharge lamp main
body 510 is H3, and the temperature Hp2 of the second electrode 93
of the comparative example is H4 which is higher than H3. The
temperature H1a and the temperature Hp2 gradually decrease with the
passage of time. At a time point T1, the temperature H1a and the
temperature Hp2 have the same value H2. If the time point T1 is
exceeded, a relationship between the temperature H1a of the
discharge lamp main body 510 and the temperature Hp2 of the second
electrode 93 of the comparative example is reversed. In other
words, the temperature Hp2 of the second electrode 93 of the
comparative example becomes lower than the temperature H1a of the
discharge lamp main body 510.
[0164] In a case where the temperature Hp2 of the second electrode
93 of the comparative example becomes lower than the temperature
H1a of the discharge lamp main body 510, if the temperature Hp2 of
the second electrode 93 is lower than the boiling point of mercury
Hg, vaporized mercury Hg easily condenses at the second electrode
93. Mercury Hg considerably easily condenses at the protrusion 541p
of the second electrode 93. Consequently, as illustrated in FIG.
13, a mercury bridge may be generated as a result of the first
electrode 92 and the second electrode 93 being connected to each
other via mercury Hg which has condensed.
[0165] In contrast, in the present embodiment, the driving current
waveform DW1 includes the heating period PH21. In the heating
period PH21, an absolute value of the driving current I of the
second polarity period P21 is greater than an absolute value of the
driving current I of the second polarity period P2 in the steady
lighting period PH1. For this reason, the second electrode 93 is
heated in the heating period PH21 more than in the steady lighting
period PH1, and thus the temperature Hp1 of the second electrode 93
increases. Consequently, as illustrated in FIG. 9, a value of the
temperature Hp1 of the second electrode 93 is H5 which is higher
than the temperature Hp2 of the second electrode 93 of the
comparative example at the time when the discharge lamp 90 is put
out.
[0166] The temperature Hp1 of the second electrode 93 of the
present embodiment decreases with the passage of time, and has the
same value (H1) as the temperature H1a of the discharge lamp main
body 510 at a time point T2. At the time when the discharge lamp 90
is put out, the value of the temperature Hp1 of the second
electrode 93 is greater than the value of the temperature Hp2 of
the second electrode 93 of the comparative example, and the time
point T2 is later than the time point T1. In other words, a time
period to reach an intersection C2 at which the relationship
between the temperature Hp1 of the second electrode 93 and the
temperature H1a of the discharge lamp main body 510 is reversed is
longer than a time period to reach an intersection C1 at which the
relationship between the temperature Hp2 of the second electrode 93
and the temperature H1a of the discharge lamp main body 510 is
reversed.
[0167] Therefore, before the intersection C2 is reached, that is,
before the temperature Hp1 of the second electrode 93 becomes lower
than the temperature H1a of the discharge lamp main body 510, the
temperature H1a of the discharge lamp main body 510 is likely to
become lower than the boiling point of Hg. As a result, according
to the present embodiment, vaporized mercury Hg easily condenses on
the inner wall of the discharge lamp main body 510, and thus
mercury Hg can be prevented from condensing at the second electrode
93.
[0168] The temperature Hp1 of the second electrode 93 increases in
a relatively short time period in the heating period PH21. For this
reason, it is possible to shorten a period in which an operation
state of the projector 500 is maintained after the user performs
the stop operation. Consequently, according to the present
embodiment, it is possible to minimize deterioration in convenience
of the projector 500.
[0169] As mentioned above, according to the present embodiment, it
is possible to provide the projector having a configuration capable
of minimizing a mercury bridge and of minimizing deterioration in
convenience.
[0170] In a case where driving power is lower than the rating power
in the steady lighting period PH1, that is, the discharge lamp 90
is driven in a low power mode, the extent of the discharge lamp 90
being cooled by the cooling device 50 is lowered. For this reason,
the temperature H1a of the discharge lamp main body 510 tends to
increase at the time when the discharge lamp is put out.
Consequently, a time period until the temperature Hp1 of the second
electrode 93 becomes lower than the temperature H1a of the
discharge lamp main body 510 after the discharge lamp 90 is put out
tends to be shortened.
[0171] In the low power mode, the first electrode 92 and the second
electrode 93 tend to grow, and the inter-electrode distance L tends
to be shortened. For this reason, the first electrode 92 and the
second electrode 93 are likely to be connected to each other via
mercury Hg which has condensed.
[0172] As described above, in a case where the discharge lamp 90 is
driven in the lower power mode in the steady lighting period PH1, a
mercury bridge is more easily generated than in a case where the
discharge lamp 90 is driven with the rating power. Therefore, the
present embodiment is notably effective in a case where the
discharge lamp 90 is driven in the low power mode in the steady
lighting period PH1.
[0173] In a case where the temperature of the periphery of the
projector 500 is high, the temperature of the discharge lamp main
body 510 is unlikely to decrease after the discharge lamp 90 is put
out. For this reason, a time period until the temperature Hp1 of
the second electrode 93 becomes lower than the temperature H1a of
the discharge lamp main body 510 is lengthened. Consequently, a
mercury bridge is more easily generated as the temperature of the
periphery of the projector 500 becomes higher. Therefore, the
present embodiment is notably effective in a case where the
temperature of the periphery of the projector 500 is high.
[0174] According to the present embodiment, since the second
electrode 93 is heated in the heating period PH21, a melting amount
of the protrusion 541p at the tip of the second electrode 93 is
increased. Thus, the inter-electrode distance L of the first
electrode 92 and the second electrode 93 is lengthened. Therefore,
even in a case where mercury Hg condenses at the protrusion 541p of
the second electrode 93, it is possible to prevent the first
electrode 92 and the second electrode 93 from being connected to
each other. In other words, according to the present embodiment, it
is possible to further minimize the occurrence of a mercury
bridge.
[0175] According to the present embodiment, the heating period PH21
is provided between the first stop operation and the second stop
operation. For this reason, it is possible to stop an operation of
the projector 500 without maintaining a state in which the
discharge lamp 90 is lighting after the user performs the second
stop operation. Therefore, according to the present embodiment, it
is possible to improve convenience of the projector 500.
[0176] According to the present embodiment, in a case where the
input reception unit 45 receives the first stop operation, a
checking operation for checking whether or not turning-off of the
supply of power to the projector 500 is necessary, that is, whether
or not putting-out of the discharge lamp 90 is necessary. For this
reason, it is possible to prevent a user from wrongly turning off
the supply of power to the projector.
[0177] According to the present embodiment, in a case where the
input reception unit 45 receives the second stop operation, the
supply of the driving current I to the discharge lamp 90 is
stopped. For this reason, it is possible to turn off the supply of
power to the projector 500 right after the user performs the second
stop operation.
[0178] According to the present embodiment, the cooling device 50
is driven in the high output mode in at least a part of the heating
period PH21. For this reason, the temperature of the discharge lamp
90, that is, both or either one of the temperature H1a of the
discharge lamp main body 510 and the temperature of the main
reflection mirror 112 can be made lower than an appropriate
temperature.
[0179] In a case where the temperature H1a of the discharge lamp
main body 510 decreases in the heating period PH21, the temperature
H1a of the discharge lamp main body 510 at the time of the
discharge lamp 90 being put out is lowered. Consequently, it is
possible to further lengthen a time period until the temperature
Hp1 of the second electrode 93 becomes lower than the temperature
H1a of the discharge lamp main body 510 after the discharge lamp 90
is put out. Therefore, according to the present embodiment, it is
possible to further minimize the generation of a mercury
bridge.
[0180] In a case where the temperature of the main reflection
mirror 112 decreases in the heating period PH21, the temperature of
the first end 90e1 of the discharge lamp is unlikely to be
maintained. Consequently, the temperature of the inner wall of the
discharge lamp main body 510 on the first end 90e1 side is likely
to be lowered, and is thus prevented from becoming higher than the
boiling point of mercury Hg. Therefore, according to the present
embodiment, it is possible to prevent mercury Hg on the first end
90e1 side from being vaporized again, and, as a result, to further
minimize the occurrence of a mercury bridge.
[0181] In the present embodiment, the following configurations and
methods may be employed.
[0182] In the present embodiment, the heating period PH21 may be
provided in a partial period between the first stop operation and
the second stop operation. In this case, the length t1 of the
heating period PH21 is appropriately set. For example, the length
t1 of the heating period PH21 is set to be equal to or more than
5.0 milliseconds (ms) and be equal to or less than 10 seconds (s).
The length t1 of the heating period PH21 is set in the
above-described way, and thus it is possible to appropriately heat
the second electrode 93 and also to prevent the second electrode 93
from being too melted.
[0183] In a case where the length t1 of the heating period PH21 is
set to a predetermined length, the input reception unit 45 may
receive the second stop operation before the heating period PH21
ends. In this case, the discharge lamp 90 is in a lighting state
until the heating period PH21 ends after the user performs the
second stop operation. However, even in this case, according to the
present embodiment, the heating period PH21 can be shortened, and
thus it is possible to minimize deterioration in convenience of the
projector 500.
[0184] In the above description, the user turns off the supply of
power to the projector 500 by performing two stop operations
including the first stop operation and the second stop operation,
but the invention is not limited thereto. In the present
embodiment, the supply of power to the projector 500 may be turned
off by performing a single stop operation. In this case, the
discharge lamp 90 is put out after the input reception unit 45
receives a stop operation and then the heating period PH21
ends.
[0185] In the present embodiment, the cooling device 50 may be
driven in the steady output mode in the heating period PH21.
[0186] In the present embodiment, the cooling device 50 may cool
only the discharge lamp 90.
[0187] In the present embodiment, a frequency of the driving
current I in the heating period PH21 may be higher than a frequency
of the driving current I in the steady lighting period PH1. In
other words, the length tp1 of the first polarity period P11 in the
heating period PH21 may be smaller than the length tp of the first
polarity period P1 in the steady lighting period PH1. The length
tn1 of the second polarity period P21 in the heating period PH21
may be smaller than the length to of the second polarity period P2
in the steady lighting period PH1. Through the setting in the
above-described way, it is possible to prevent the protrusion 541p
of the second electrode 93 from being rapidly melted and being
deformed, and thus to stably further increase the temperature Hp1
of the second electrode 93 in the heating period PH21.
[0188] In the present embodiment, an absolute value of the driving
current I of the first polarity period P11 in the heating period
PH21 may be greater than an absolute value of the driving current I
of the first polarity period P1 of the steady lighting period PH1.
According to the configuration, it is possible to further melt the
first electrode 92 in the heating period PH21 and thus to further
lengthen the inter-electrode distance L. Consequently, it is
possible to further minimize the occurrence of a mercury
bridge.
[0189] In the first polarity period P11 and the second polarity
period P21 of the heating period PH21, driving power supplied to
the discharge lamp 90 can be made the same. Therefore, there is no
time and effort to change driving power supplied to the discharge
lamp 90 in the heating period PH21, and this is convenient. Since
driving power is not changed in the heating period PH21, it is
possible to minimize the occurrence of flickering in the discharge
lamp 90.
[0190] In the present embodiment, there may be a configuration in
which, for example, a capacitor or a battery is incorporated into
the circuit configuration of the projector 500, and the driving
current I is supplied to the discharge lamp 90 from the capacitor
or the battery in the heating period PH21. According to the
configuration, for example, even in a case where a method is
employed in which the supply of power to the projector 500 is
turned off by directly pulling out a plug for supplying power to
the projector 500, the heating period PH21 can be provided. In this
case, directly pulling out the plug corresponds to a stop
operation. The input reception unit 45 receives the stop operation
by detecting that the supply of main power is stopped.
[0191] In the above description, a value of the driving current I
of the second polarity period P21 in the heating period PH21 is
-Im2 as a constant value, but the invention is not limited thereto.
In the present embodiment, an absolute value of the driving current
I of the second polarity period P21 in the heating period PH21 may
be changed within a range greater than an absolute value of the
driving current I of the second polarity period P2 in the steady
lighting period PH1.
[0192] In the present embodiment, a plurality of heating periods
PH21 may be provided. In this case, after a stop operation is
received, the heating period PH21 and the steady lighting period
PH1 are alternately repeated. According to the configuration, it is
possible to appropriately increase the temperature Hp1 of the
second electrode 93 and also to prevent the protrusion 541p of the
second electrode 93 from being depleted.
Second Embodiment
[0193] A second embodiment is different from the first embodiment
in terms of a current waveform.
[0194] In the following description, the same constituent elements
as in the first embodiment are given the same reference numerals,
and description thereof will be omitted in some cases.
[0195] FIG. 10 is a diagram illustrating an example of a driving
current waveform DW2 of the present embodiment. FIG. 10 illustrates
the driving current waveform DW2 before and after the input
reception unit 45 receives a stop operation.
[0196] As illustrated in FIG. 10, the driving current waveform DW2
(driving current I) includes the steady lighting period PH1 and a
heating period (second AC period) PH22. In the present embodiment,
the driving current waveform DW2 transitions from the steady
lighting period PH1 to the heating period PH22 when the input
reception unit 45 receives the first stop operation.
[0197] The heating period PH22 alternately includes a first
polarity period P12 in which the first polarity state occurs and
the second polarity period P21 in which the second polarity state
occurs.
[0198] In the present embodiment, a value of the driving current I
of the first polarity period P12 is, for example, Im3. An absolute
value of Im3 is smaller than an absolute value of Im1. In other
words, an absolute value of the driving current I of the first
polarity period P12 in the heating period PH22 is smaller than an
absolute value of the driving current I of the first polarity
period P1 in the steady lighting period PH1.
[0199] In the present embodiment, for example, a difference between
an absolute value of Im1 and an absolute value of Im3 is the same
as a difference between an absolute value of -Im2 and an absolute
value of -Im1. In other words, a decrease amount of driving power
of the first polarity period P12 relative to driving power of the
first polarity period P1 is the same as an increase amount of
driving power of the second polarity period P21 relative to driving
power of the second polarity period P2. Consequently, a mean value
of driving power supplied to the discharge lamp 90 in the heating
period PH22 is the same as a value of driving power supplied to the
discharge lamp 90 in the steady lighting period PH1.
[0200] A length tp2 of the first polarity period P12 may be set to
be the same as the length tp1 of the first polarity period P11 of
the first embodiment.
[0201] A length t2 of the heating period PH22 may be set to be the
same as the length t1 of the heating period PH21 of the first
embodiment.
[0202] Configurations other than the above description are the same
as the configurations of the first embodiment.
[0203] According to the present embodiment, an absolute value of
the driving current I of the first polarity period P12 in the
heating period PH22 is smaller than an absolute value of the
driving current I of the first polarity period P1 in the steady
lighting period PH1. For this reason, a value of mean driving power
in the heating period PH22 can be made close to a value of driving
power in the steady lighting period PH1. Consequently, it is
possible to minimize the occurrence of flickering in the discharge
lamp 90 when a period in which an alternating current is supplied
to the discharge lamp 90 transitions from the steady lighting
period PH1 to the heating period PH22.
[0204] According to the present embodiment, a mean value of driving
power supplied to the discharge lamp 90 in the heating period PH22
is the same as a value of driving power supplied to the discharge
lamp 90 in the steady lighting period PH1. Consequently, it is
possible to further minimize the occurrence of flickering in the
discharge lamp 90 when a period in which an alternating current is
supplied to the discharge lamp 90 transitions from the steady
lighting period PH1 to the heating period PH22.
[0205] In the present embodiment, the following configurations and
methods may be employed.
[0206] In the present embodiment, a difference between an absolute
value of Im1 and an absolute value of Im3 may be different from a
difference between an absolute value of -Im2 and an absolute value
of -Im1. In other words, a mean value of driving power supplied to
the discharge lamp 90 in the heating period PH22 may be different
from a value of driving power supplied to the discharge lamp 90 in
the steady lighting period PH1.
[0207] In the present embodiment, a value of the driving current I
of the first polarity period P12 in the heating period PH22 may be
changed.
Third Embodiment
[0208] A third embodiment is different from the first embodiment in
that a length of a second polarity period is larger than a length
of a first polarity period in a heating period. In the following
description, the same constituent elements as in the first
embodiment are given the same reference numerals, and description
thereof will be omitted in some cases.
[0209] FIG. 11 is a diagram illustrating an example of a driving
current waveform DW3 of the present embodiment. FIG. 11 illustrates
the driving current waveform DW3 before and after the input
reception unit 45 receives a stop operation.
[0210] As illustrated in FIG. 11, the driving current waveform DW3
includes the steady lighting period PH1 and a heating period PH23
in which an alternating current is supplied to the discharge lamp
90. In the present embodiment, the driving current waveform DW3
transitions from the steady lighting period PH1 to the heating
period PH23 when the input reception unit 45 receives the first
stop operation.
[0211] In the present embodiment, the heating period PH23 is
entirely provided after the input reception unit 45 receives the
first stop operation until receiving the second stop operation. In
other words, a length t3 of the heating period PH23 corresponds to
a time period after a user performs the first stop operation until
performing the second stop operation.
[0212] The heating period PH23 alternately includes a first
polarity period P13 in which the first polarity state occurs and a
second polarity period P23 in which the second polarity state
occurs. In other words, in the heating period PH23, an alternating
current is supplied to the discharge lamp 90.
[0213] A value of the driving current I of the first polarity
period P13 is Im1. In other words, the value of the driving current
I of the first polarity period P13 is the same as a value of the
driving current I of the first polarity period P1 in the steady
lighting period PH1.
[0214] A value of the driving current I of the second polarity
period P23 is -Im1. In other words, the value of the driving
current I of the second polarity period P23 is the same as a value
of the driving current I of the second polarity period P2 in the
steady lighting period PH1.
[0215] A value of driving power in the steady lighting period PH1
is the same as a value of driving power in the heating period
PH23.
[0216] A length tn3 of the second polarity period P23 in the
heating period PH23 is larger than a length tp3 of the first
polarity period P13 in the heating period PH23. Here, in the
example illustrated in FIG. 11, a frequency of the driving current
I in the heating period PH23 is the same as a frequency in the
steady lighting period PH1. In other words, a duty ratio of the
second polarity period P23 is higher in the heating period PH23
than in the steady lighting period PH1.
[0217] A ratio of the length tn3 of the second polarity period P23
in the heating period PH23 to the length tp3 of the first polarity
period P13 in the heating period PH23 may be, for example, 3 or
more and 9 or less. In other words, a duty ratio of the second
polarity period P23 in the heating period PH23 may be, for example,
0.75 or more and 0.9 or less. Since the length tn3 of the second
polarity period P23 in the heating period PH23 is set in the
above-described way, it is possible to appropriately heat the
second electrode 93 and also to prevent the second electrode 93
from being depleted.
[0218] Other configurations of the heating period PH23 may be the
same as the configurations of the heating period PH21 of the first
embodiment.
[0219] The control device 40 controls the discharge lamp driving
unit 230 according to the above-described driving current waveform
DW3.
[0220] The above-described embodiment may be expressed as a control
method for the projector. In other words, a control method for the
projector of the present embodiment includes causing the discharge
lamp 90 to emit light; causing the main reflection mirror 112 to
reflect the light emitted from the discharge lamp 90 in the
irradiation direction D; and causing the input reception unit 45 to
receive a predetermined operation, in which the discharge lamp 90
includes the discharge lamp main body 510 having the discharge
space 91 therein, and the first electrode 92 and the second
electrode 93 protruding in the discharge space 91, in which the
main reflection mirror 112 is attached to the first end 90e1 of the
discharge lamp main body 510, the first electrode 92 is disposed on
the first end 90e1 side, and the second electrode 93 is disposed on
the second end 90e2 side of the discharge lamp main body 510 on an
opposite side to the first end 90e1, in which the driving current I
includes the steady lighting period PH1 and the heating period PH23
in which an alternating current is supplied to the discharge lamp
90, in which the steady lighting period PH1 and the heating period
PH23 alternately include the first polarity periods P1 and P13 in
which the first electrode 92 serves as an anode and the second
polarity periods P2 and P23 in which the second electrode 93 serves
as the anode, in which, in a case where the input reception unit 45
receives a stop operation on the projector, a period in which an
alternating current is supplied to the discharge lamp 90
transitions from the steady lighting period PH1 to the heating
period PH23, and in which the length tn3 of the second polarity
period P23 in the heating period PH23 becomes larger than the
length tp3 of the first polarity period P13 in the heating period
PH23.
[0221] According to the present embodiment, the driving current
waveform DW3 includes the heating period PH23. In the heating
period PH23, the length tn3 of the second polarity period P23 is
larger than the length tp3 of the first polarity period P13. For
this reason, in the heating period PH23, the temperature Hp1 of the
second electrode 93 which is heated more than in the steady
lighting period PH1 becomes higher. Consequently, according to the
present embodiment, in the same manner as in the first embodiment,
it is possible to provide the projector having a configuration
capable of minimizing a mercury bridge and of minimizing
deterioration in convenience.
[0222] In the present embodiment, a frequency of the driving
current I in the heating period PH23 may be higher than a frequency
of the driving current I in the steady lighting period PH1.
According to the configuration, the second electrode 93 is likely
to be gradually heated, and it is possible to prevent the
protrusion 541p of the second electrode 93 from being melted away
due to a steep heat load. The frequency of the driving current I in
the heating period PH23 is preferably equal to or higher than, for
example, 500 Hz and is equal to or lower than 1 kHz. Through the
setting in the above-described way, it is possible to prevent a
steep heat load from being applied to the second electrode 93 and
also to increase the temperature Hp1 of the second electrode 93
relatively fast.
[0223] As described in the first to third embodiments, in an aspect
of the invention, configurations and methods thereof are not
particularly limited as long as the temperature Hp1 of the second
electrode 93 can be made higher by increasing a heat load applied
to the second electrode 93 in the heating period. In other words,
an absolute value of the driving current I supplied to the
discharge lamp 90 in the second polarity period may be great as in
the first embodiment and the second embodiment, and the length of
the second polarity period may be large as in the third
embodiment.
[0224] In the first to third embodiments, a description has been
made of an example of a case where the invention is applied to the
transmissive projector, but the invention is applicable to a
reflective projector. Here, the term "transmissive" indicates a
type in which a liquid crystal light valve including a liquid
crystal panel or the like transmits light therethrough. The term
"reflective" indicates a type in which the liquid crystal light
valve reflects light. A light modulation device is not limited to a
liquid crystal panel or the like, and may be a light modulation
device using, for example, a micro-mirror.
[0225] In the first to third embodiments, a description has been
made of an example of the projector 500 using the three liquid
crystal panels 560R, 560G and 560B (the liquid crystal light valves
330R, 330G and 330B), but the invention is applicable to a
projector using only a single liquid crystal panel, and to a
projector using four or more liquid crystal panels.
[0226] The configurations of the first to third embodiments may be
combined with each other as appropriate so as not to cause
contradiction therebetween.
* * * * *